Battery driven electronic equipment, e.g. mobile electronic equipment, such as equipment positioned in vehicles, can be subjected to high energy voltage transients, e.g. if the battery is accidentally disconnected from an alternator charging circuit. Such voltage transients are sometimes referred to as ‘load-dump transients’, and they may cause severe damage to the equipment. It is therefore desirable to protect the equipment from such transients.
In the prior art, three different approaches have been used in order to protect electronic equipment from load-dump transients.
A bi-directional diode positioned at the input of the electronic unit.
A MOSFET positioned in the positive rail of the battery.
A relay positioned in the positive rail of the battery.
Although providing the desired protection, all of these solutions result in the use of relatively bulky components which additionally introduce substantive power losses in the electric circuit. Accordingly, a bulky and energy consuming circuit is the result. This is very disadvantageous.
Furthermore, it is desirable to maintain the possibility of protecting the electronic application from damages occurring in the case that an alternator charging circuit is accidentally connected to the DC power source with a reversed polarity. In this case the circuit should be interrupted, thereby preventing a current from running in the circuit. This may be done using a field effect transistor (FET).